The present invention relates to thermal transfer printing media and, more particularly, to a thermal transfer printing medium useful in printing images onto a colored image-receiving medium.
Conventionally, the thermal transfer technology has been utilized for forming print images solely on white paper sheets. Recently, however, the thermal transfer technology has found increasing applications such as in forming heading labels, name labels and backbone labels.
In these applications, printed images are frequently formed on colored image-receiving media; for instance, white characters are formed on a black image-receiving medium.
A conventional thermal transfer printing medium having a white heat-meltable ink layer, however, has been able to provide only grayish print images when used in printing onto a black image-receiving medium.
Such a conventional white heat-meltable ink layer typically employs titanium oxide as a white pigment. Although titanium oxide per se has a great hiding power, limitations are imposed on the content of titanium oxide in the heat-meltable ink layer and the thickness of the ink layer for ensuring a satisfactory transferability of the ink layer and, hence, the hiding power of the whole ink layer cannot be enhanced.
On the other hand, there has been proposed in the prior art the enhancement of print density by providing a metal deposition layer on a color ink layer of a thermal transfer printing medium to cut off reflected light from a recording paper sheet (refer to Japanese Unexamined Patent Publication No. 92492/1988).
Print images provided by this thermal transfer printing medium are surely not affected by the color of an image-receiving medium, but the images are influenced by the metal deposition layer serving as a hiding layer. For this reason, such a thermal transfer printing medium still involves a problem of impossibility of providing print images in a color inherent to the color ink layer. Specifically, where the metal deposition layer is an aluminum deposition layer and the color ink layer is, for example, a white ink layer, resulting print images are in a grayish color with their whiteness degraded.
In view of the foregoing, it is an object of the present invention to provide a thermal transfer printing medium capable of forming print images which are affected by neither the color of an image-receiving medium nor a metal deposition layer serving as a hiding layer and which are in a color inherent to a color ink layer.
This and other objects of the present invention will become apparent from the description hereinafter.